1. Field of the Invention
The present invention relates to a roll feed apparatus which is suited to use in, for example, automatic manufacturing machines for manufacturing goods through a plurality of steps and, more particularly, to a roll feed apparatus of the type having a pair of rolls adapted for clamping therebetween a sheet material such as to feed the sheet material from one to another working station.
2. Description of the Prior Art
A known roll feed apparatus of the type mentioned above has a first roll integrally carried by a first shaft for oscillatory rotation therewith, a second roll integrally carried by a second roll shaft for oscillatory rotation in the direction counter to that of the first roll and adapted for cooperation with the first roll in clamping therebetween a sheet material such as to feed the sheet material, and a roll release means adapted to move both rolls relatively away from each other when the rolls rotate in the direction counter to the feeding direction thereby unclamping the sheet. This type of roll feed apparatus is shown, for example, in Japanese Utility Model Laid-Open No. 67831/1983.
Preferably, this type of roll feed apparatus has a function for varying the clamping force exerted by both rolls in accordance with the thickness and kind of material of the sheet to be fed, in order to avoid any deformation and breakage of the sheet.
From this point of view, the roll feed apparatus disclosed in Japanese Utility Model Laid-Open No. 67831/1983 discloses a first adjusting means for controlling the force by which the first roll is pressed towards the second roll thereby adjusting the clamping force exerted on the sheet by both rolls, and a second adjusting means for optimizing the roll gap for the thickness of the sheet to be fed.
This roll feed apparatus, however, involves a problem in that the optimization of the clamping force for various sheet thicknesses is not easy to conduct, due to difficulty in effecting a minute control of the roll gap.